Plugable media stack loading system

ABSTRACT

A media stackloader processes removable data storage media such as optical disks, magnetic diskettes, or tape media. The stackloader removably couples to a storage drive, such as by plugging into a slot of the host computer. The stackloader has a plug portion integral with a housing portion, the plug portion plugging into the host computer and the housing portion housing a magazine containing the removable media. The stackloader includes a device for moving the magazine vertically within the housing to align selected cartridges with an opening in one of the drives of the personal computer. After the cartridge is aligned, a device is employed for moving the cartridge horizontally into the drive for processing and, after processing, for withdrawing the cartridge from the drive back into the magazine. A locking mechanism selectively locks and unlocks the cartridges to prevent improper removal of cartridges from the magazine. Another aspect of the invention includes a method for operating a media stackloader, supporting operations needed to add new cartridges to a magazine, remove existing cartridges, read data from a cartridge, write data to a cartridge, audit the status of cartridges in a magazine, and aid the operator in exchanging mounted magazines and cartridges with different, un-mounted magazines or cartridges.

This application is a division of application Ser. No. 08/577,948, filedDec. 22, 1995, now U.S. Pat. No. 5,757,594.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the exchange of data between computersand removable digital data storage media such as optical disks. Moreparticularly, the invention concerns a plugable media stackloaderapparatus that can be plugged into a slot of a host computer forprocessing media in a drive of the host computer. Another aspect of theinvention concerns a process for operating the stackloader and the hostcomputer to manage, maintain, and utilize storage media of thestackloader.

2. Description of the Related Art

To store large amounts of data under conditions guaranteeing automatic,reasonably speedy access to data storage media, media libraries havebeen developed. These libraries store the media in magazines and employtransport mechanisms to move media instances between magazines and mediadrives.

Magazines containing media, such as cartridges which contain optical ormagnetic disks, are presently processed by large and complex transportsystems. An operator inserts a magazine into a receptacle whichpositions cartridges in the magazine for processing. A picker transportsa selected cartridge from the magazine to a drive where a disk containedin the cartridge is processed by writing and reading data on the disk.After processing, the cartridge is transported to the magazine and thepicker stands ready to transport another cartridge. The picker for sucha transport system is somewhat complex. The picker grabs and withdrawsthe cartridge from the magazine in an X direction, transports it in a Zdirection and inserts the cartridge in the drive in the X direction.Normally the picker includes a receptacle through which the cartridge istranslated between the magazine and the drive without any flipping ofthe cartridge.

There has been a long standing and strong felt need in small, low-endcomputer systems for a media storage and transport system that providesa magazine mounted library capability without requiring additional driveor a standalone library. What has been described hereinabove is a largesystem employed by companies or other entities which have a large volumeof data to be processed. Such a system is too large and too expensivefor a small system which processes data on a personal computer. It isobvious that the scheme of the large system is not applicable forprocessing magazine mounted media by a personal computer. To becompatible with a personal computer the apparatus must be small, easy touse and low in cost.

In small computer systems, stackloaders have been developed to providelibrary-like services for media such as tape or floppy disks.Stackloaders typically store a plurality of medium instances (such astape cassettes) in a vertical array (a "stack") by means of a frame,which may be plugged into a medium drive receptacle. A transportmechanism selects a medium instance, extracts it from the stack, loadsit into the drive, and later extracts it from the drive and returns itto the stack.

To date, stackloaders for small computer systems have been particularlyadapted for a single use. Relatedly, no stackloader is known which caneither plug into a drive receptacle or operate on a standalone basis.Further, the existing stackloaders are not capable of accessing mediuminstances in adjacent receptacles. Last, known stackloaders are designedfor use with particular medium configurations and cannot adapt to thedifferent distances and dimensions of other configurations. Thus, thereis a manifest need for a stackloader that can interface with a smallcomputer system by anchoring in a drive receptacle, yet which can storemedium instances and operate outside of the drive receptacle and accessmedium instances in adjacent drive receptacles. The need also embracesthe as-yet unsatisfied requirement that the stackloader be adaptivelyreconfigurable to the dimensions and distances of different mediumconfigurations.

SUMMARY OF THE INVENTION

The present invention provides a novel transport system for processing abatch of cartridges in a storage drive, such as a drive of a personalcomputer. The transport system, which is referred to as a plugablestackloader (or a plugable autochanger), includes a housing foraccepting a magazine of cartridges and a plug which fixedly extends fromthe housing. The plug plugs into a slot or half high slot in the frontface of the computer with the housing positioned opposite a drive forprocessing the cartridges. A vertical transport device verticallypositions the magazine within the housing at selected vertical positionswhich align a selected cartridge with the drive. When the selectedcartridge is aligned, a horizontal picker device moves the cartridgeinto the drive for processing and returns the cartridge to the magazineafter processing.

The vertical transport device and the horizontal picker device arecontrolled by an autochanger controller which may be located inside theplug portion of the stackloader. The autochanger controller is connectedto a motherboard in the personal computer via a Small Computer SystemInterface ("SCSI"). An operator can control the operation of thestackloader by sending commands to the computer via a keyboard. Selecteddata can be retrieved, recorded or sorted. If the plugable stackloaderis not involved in an operation, an operator can add or removecartridges from the magazine.

Provision is made for indicating the type of magazine and media, whetherthe magazine is at a home position and whether a cartridge is in thedrive. The vertical movement device and the horizontal movement deviceemploy incremental movements which can be counted to various levels sothat the stackloader can be adapted to process various types of media.In a preferred embodiment, the drive receives a major portion of thecartridge while a small portion of the cartridges remains outside thedrive in engagement with the horizontal picker device. This arrangementenables a very simple horizontal picker device. A major differencebetween the present invention and large magazine transport systems isthat in the present invention the magazine is transported vertically.

Advantageously, the stackloader includes a locking mechanism, such as asolenoid, to selectively prevent removal of cartridges during certainsensitive operations, such as when a cartridge is being transportedwithin the stackloader. Also, an indicator strip is provided adjacentthe cartridge receptacles, to aid the operator in locating a cartridgereceptacle for removal or addition of a cartridge, by individuallyactivating the indicator proximate the appropriate receptacle. Also, ina multiple stackloader system, assistance may be provided to theoperator in adding or removing a magazine by illuminating all indicatorsof the indicator strip of the stackloader where the magazine exchange isto take place. Operator interaction is enhanced by use of an accesspanel mounted near the stackloader, to receive input from the operatorand provide messages to the him/her.

Another important aspect of the invention includes a process foroperating a pluggable stackloader such as the embodiment describedherein. Operational sequences are provided for adding a new cartridge toa magazine, removing a cartridge, auditing the status of the cartridges,reading data from a cartridge, and writing data to a cartridge.Moreover, a sequence is provided that aids the operator in exchangingcartridges with a magazine mounted to the stackloader, or in exchangingthe magazine itself with a different magazine.

The invention provides a number of distinct advantages to its uses. Forexample, the stackloader implementation of the invention allows theinsertion or removal of a magazine or cartridge using a set of sensorsand interlocks such that a magazine or cartridge can be inserted orremoved from the stackloader free from danger to the operator or damageto the media or machine. The invention also provides a number of otherbenefits, as shown below.

DESCRIPTION OF THE DRAWINGS

The nature, objects, and advantages of the invention will become moreapparent to those skilled in the art after considering the followingdetailed description in connection with the accompanying drawings, inwhich like reference numerals designate like parts throughout, wherein:

FIG. 1A is a block diagram generally depicting an illustrative system ofvarious electronic components and software modules, as well as theelectrical and functional interconnections therebetween.

FIG. 1 is a side elevational schematic illustration of the plugablestackloader plugged into a personal computer.

FIG. 2 is a schematic illustration of a cartridge which has a pair ofnotches.

FIG. 3 is an isometric view of the plugable stackloader plugged into apersonal computer with a cartridge locking device shown in the lockedposition.

FIG. 4 is the same as FIG. 3 except the cartridge locking device isshown in an unlocked position.

FIG. 4A is an enlarged front face view of the operator panel shown inFIGS. 3-4.

FIG. 5 is a side elevational schematic illustration of a first side ofthe plugable stackloader plugged in a personal computer with a sidecover removed.

FIG. 6 is a second side view of the magazine out of the housing of thestackloader with one cartridge shown in place.

FIG. 7 is a side elevational schematic illustration of a second side ofthe plugable stackloader plugged into a personal computer with the sidecover removed and with a horizontal cartridge moving device shown in aretracted position.

FIG. 8 is the same as FIG. 7 except the horizontal cartridge movingdevice is shown in an extended position.

FIG. 9 is a block diagram of an autochanger controller.

FIG. 10 is a block diagram of logic of the autochanger controller.

FIG. 11 is a flow diagram for entering or exiting a cartridge ormagazine from the stackloader.

FIG. 12 is a side elevational schematic illustration of the plugablestackloader in a standalone configuration.

FIG. 13 is a flow diagram illustrating an example of an overall routinefor performing data access pursuant to the invention.

FIG. 14 is a flow diagram illustrating an example of a routine foradding a cartridge to the stackloader of the invention.

FIG. 15 is a flow diagram illustrating an example of a routine forremoving a cartridge from the stackloader of the invention.

FIG. 16 is a flow diagram illustrating an example of a routine forauditing inventory pursuant to the invention.

FIG. 17 is a flow diagram illustrating an example of a routine forreading data from, and writing data to cartridges using the pluggablestackloader of the invention.

FIG. 18 is a diagram of an exemplary data storage device in accordancewith one aspect of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hardware Components &Interconnections

FIG. 1A generally depicts an illustrative system 10 in accordance withthe present invention, including various electronic components andsoftware modules and the electrical and functional interconnectionstherebetween. The system 10 includes a host computer 38, which comprisesa digital data processing machine such as a workstation, mainframecomputer, personal computer, or other appropriate platform. As describedin greater detail below, the host computer 38 is coupled to astackloader 20, which selectively loads and accesses cartridgescontained in a magazine coupled to the stackloader.

The host computer 38 is also coupled to a keyboard display 50, toexchange data between the host computer 38 and a human operator (notshown). In this respect, the keyboard display 50 may include (1) a videomonitor or other apparatus to visually convey human-readable informationto the operator from the host computer 38, and (2) a keyboard or otherdata entry device to convey machine-readable information from theoperator to the host computer 38. However, the keyboard display 50 mayalternatively comprise a variety of other operator interface devices.

The host computer 38 has a number of sub-components. Centrally, the hostcomputer 38 includes a host operating system 11, which may be a softwaremodule such as OS/2, VMS, or another suitable operating system. Theoperating system 11 functionally interconnects to an application program12, a local area network ("LAN") support unit 13, a stackloadercontroller 14, and a fast-access storage unit 15. If desired, thecomponents 11-14 may be implemented by a single processing unit, such asthe CPU (not shown) of the host computer 38. As an alternative, thecomponents 11-14 may be implemented by one or more separate hardwarecomponents.

The application program 12 comprises a program executed by the hostcomputer 38 to perform some complex task requested by the operator viathe keyboard display 50. To most thoroughly illustrate the features ofthe present invention, the application program 12 is discussed herein asbeing a program that requires access to data accessible by thestackloader 20. Such an application program may comprise a databaseprogram, for example.

The LAN support unit 13, an optional feature, interfaces with a LAN bus17 that ties the host computer 38 to other remotely located hosts, suchas the remote host 21, also participating in the LAN.

The fast-access storage unit 15 comprises a data storage device, such asa Direct Access Storage Device ("DASD"), to quickly exchange databetween the host computer 38 and one or more data storage media (notshown) included in the storage unit 15. For example, the storage unit 15may comprise a magnetic "hard drive".

The stackloader controller 14 assists in directing the stackloader 20 tostore and retrieve data pursuant to the invention. The construction ofthe stackloader 20 is described in greater detail below. The stackloadercontroller 14 may be located remotely from the stackloader 20 itself,whereas an autochanger controller 16 may be provided locally aboard thestackloader 20. Alternatively, the controllers 14 and 16 mayincorporated into a single unit.

As illustrated below, some of the many functions of the stackloadercontroller 14 are to maintain an inventory that lists all magazines andcartridges, evaluate requirements for delivery of magazines andcartridges to the stackloader 20, and oversee the exchange of databetween the host computer 38 and the media via the drive 26, e.g.reading and writing. In this respect, the stackloader controller 14 maybe considered to include (1) a device driver (not shown) thatcommunicates with the drives and the library to access the media andmove the cartridges, (2) a volume and file driver (not shown) thatinterfaces with the device driver to read and write directoryinformation and data, (3) a library inventory driver that accesses theinventory information and interfaces with a library driver to cause therequested volume to be fetched and mounted in the library, and alsofacilitates communications between the volumes contained in the libraryand the applications and operator.

The autochanger controller 16 communicates with the stackloadercontroller 14 via an interface, described for illustrative purposes asan SCSI 48. Operation of an SCSI, including optical disk drive SCSIcommands and autochanger SCSI commands, is described in a published ANSIStandard entitled "Small Computer System Interface--2, X3T9.2/86-109".Although an SCSI is preferred, a variety of other interfaces may be usedinstead. A drive 26 communicates with the stackloader controller 14 viathe SCSI 48, or via a separate interface (not shown) if desired. Thedrive 26 preferably comprises one or more data storage drives forreading and writing data to storage-media such as optical disks and/ormagnetic disks.

As explained in greater detail below, the stackloader 20 serves tomanage the physical transfer of data storage media between a multi-mediastorage structure (such as a magazine) and the data storage drive 26. Inthis regard, the system 10 may include multiple magazines 22, which maybe individually coupled to the stackloader 20 to make the cartridges ofthese magazines accessible by the stackloader 20. Machinery (describedbelow) of the stackloader 20 selectively loads media from thestackloader 20 into the data storage drive 26, permitting the drive 26to read and write data from/to the loaded media.

More particularly, the stackloader 20 may advantageously be "pluggedinto" a full height or "half high" 51/4 inch slot in the face of apersonal computer that has one or more storage drives in one or moreslots therebelow. As described below, the stackloader 20 employs avertical moving device to move a magazine up and down within thestackloader so that an item of media can be aligned with an opening in aselected drive(s). A horizontal moving device moves media items into andout of the drive(s).

FIG. 1 illustrates a specific example of the stackloader 20, shownplugged into the computer 38 for processing media 24 in the drive 26. Asmentioned above, the drive 26 may comprise an optical drive 27 or afloppy drive 28, for example. The stackloader includes a housing 30 anda plug 32, the plug 32 being fixedly attached to the housing 30 andcoextensive along its sides and top with the housing which will be clearfrom the drawings described hereinafter. The plug 32 is snugly receivedby a slot, such a 51/4 inch slot 34 of the computer so that a rear face36 of the housing is facing and adjacent a front face 37 of the computer38.

The media 24, which will be referred to hereinafter as cartridges, aremounted in receptacles in a magazine 40 so that a cartridge can slidefrom the magazine into a drive when the cartridge is aligned therewith.Although the preferred embodiment contemplates each cartridge 24comprising a portable container housing a single optical disk, the terms"media" and "cartridges" used herein also include optical tape, magneticdiskettes, magnetic tape, or any other removable media.

Provision is made for vertically moving the magazine 40 for aligning aselected cartridge with a drive and provision is made for horizontallymoving the aligned cartridge into and out of the drive for processingwhich will be explained in more detail hereinafter. One aim of theinvention is to process a mini-library of cartridges with a typicalpersonal computer upon command.

The autochanger controller ("A.C.C.") 16 is located inside the plug 32and is connected by a cable 44 to the stackloader controller 14 via theSCSI 48. In the illustrated embodiment, the stackloader controller 14 isembodied in a motherboard 46 of the computer 38. The details of thesecomponents will be described in more detail hereinafter. The userkeyboard display 50 may be connected to the motherboard 46 asillustrated, and employed by an operator to send commands via thecomputer motherboard 46 and the SCSI 48 to the stackloader 20 forvertically moving the magazine 40 and horizontally moving the cartridges24. The SCSI interface may comprise a circuit board commonly used withinmost personal computers and the autochanger controller 16 may comprise astandard microprocessor for media libraries. The SCSI 48 and theautochanger controller 16 preferably employ the ANSI standard commandset for media libraries.

FIG. 2 is a schematic illustration of a preferred cartridge 24 forcontaining a medium such as an optical disk 52. The cartridge has a pairof parallel side edges 54 and 56 which have oppositely located notches60 and 62, respectively. While the invention is primarily described foroptical disks, it should be understood that the invention could beemployed for magnetic media.

In FIG. 3 the plug 32 of the stackloader 20 is shown plugged into theslot 34 of the computer as described hereinabove. The stackloader 20 hasright and left cover plates 64 and 66 which cover support plates, to bedescribed hereinafter, and which provide right and left vertical sidesof the housing 30 and the plug 32. A rear portion of the magazine 40 andrear portions of the cartridges 24 are seen adjacent a rear opening 68of the stackloader housing. The right and left notches 60 and 62 (FIG.2) of the cartridges are vertically aligned on right and left sides,respectively, of the housing 30. A rail 70 is received by the rightnotches 60 for locking the cartridges from horizontal movement along anx-axis as the magazine is moved vertically along a z-axis. There is oneexception to this locking function. The rail 70 is provided with a notch72 which is aligned with an opening in the drive 26 so that when themagazine 40 is vertically positioned to align a selected cartridge withthe opening of the drive the cartridge can be moved horizontally intothe drive for processing. In order to unlock the cartridges for removaland replacement, the rail 70 is made integral with a flange 74, which ispivoted to the housing at 76, for allowing the rail 70 to swingoutwardly from the notches as illustrated in FIG. 4.

Right and left transversely extending tabs 78 and 80 are also alignedwith the opening in the drive to prevent an operator from inserting acartridge into an empty receptacle which is reserved for a cartridgewhich is being processed in the drive. The operator can remove andreplace cartridges in receptacles of the magazine either above or belowthese tabs 78 and 80. The tab 78 may be pivoted at 81 and the tab 80 maybe connected to the rail 70 so that they can be swung out of the waymaking a passageway for inserting and removing magazines from thehousing. With the magazine removed the operator can put a cartridgedirectly into a drive or take a cartridge out of a drive.

A portion of the magazine and cartridges are cut away in FIG. 3 to showa engagement block 82 which is received in the vertical column of leftnotches 62 of the cartridges as the cartridges move up and down withinthe magazine 40. The engagement block 82 is horizontally aligned with anopening in the drive 26 so that when a selected cartridge is alignedwith the opening in the drive, the detent can be moved horizontally formoving the cartridge into the drive 26 for processing. The engagementblock 82 is connected to a horizontal movement device, a portion ofwhich is shown at 84 and which will be described in more detailhereinafter.

As shown in FIGS. 3-4, the stackloader 20 also includes a lockingsolenoid 194 (also called a "door lock solenoid"), a locking tab 191,and a ready sensor 193. The locking solenoid 194 comprises anelectrically-operated solenoid positioned near the locking tab 191, thetab 191 being firmly connected to, or integral with, the flange 74. Whenthe stackloader is operating, the locking solenoid 194 is used inconjunction with the rail 70 (as shown in FIG. 3) for keeping the railin a locked position in the notches 60 of the cartridges 24.

The locking solenoid 194 is electrically connected to a current driverof the autochanger controller 16, as described below; when the lockingsolenoid 194 receives an activating electrical signal from its currentdriver, a locking pin extends from its recessed position 194a to itslocking position 194b and prevents the locking tab 191 from pivotingoutward. In this position, the flange 74 cannot pivot outward to exposethe cartridges 24. Accordingly, the cartridges 24 are locked in placewhen the locking solenoid 194 is activated.

The ready sensor 193 comprises a mechanical, opto-electric, or anotherappropriate device to sense whether the flange 74 is completely closed.In the illustrated embodiment, the ready sensor 193 comprises aresilient button that is depressed and thus activated when the lockingtab 191 pivots against the sensor 193.

Another component of the stackloader 20 is an indicator strip 195. Theindicator strip 195 highlights one or more cartridge receptacles in themagazine by providing a visible indication next to the receptacles. Inaccordance with the invention, this is performed to indicate when it issafe or desirable to remove cartridges from the highlighted receptacles,or to insert cartridges into the highlighted receptacles, for instance.In this respect, the indicator strip 195 may comprise a long, narrowstrip of LEDs 195a (as illustrated), or another suitable selectivelyactivated visual indicator(s).

The indicators 195a are preferably spaced at a sufficiently smallinterval to accommodate magazines containing many small media therein,and also to accommodate magazines containing a lesser number of largersized media. In addition to the functions described above, multipleindicator strips 195 may be employed in a data storage system withmultiple stackloaders, where all indicators 195a of a single strip 195are illuminated simultaneously to direct an operator's attention to aparticular stackloader to conduct magazine exchange therein.

Referring to FIGS. 3-4 and 4A, the stackloader 20 also includes anoperator panel 85 to exchange data between the operator (not shown) andthe stackloader 20. More particularly, the operator panel 85 includes(1) visual indicators 196 to visually convey human-readable informationto the operator from the stackloader 20, and (2) switches 197, such aspush-buttons, to convey machine-readable information from the operatorto the stackloader 20. The visual indicators 196 preferably compriselight-emitting diodes ("LEDs"), or another suitable visual display, toprovide various items of information to the operator.

In the illustrated example, the indicators 196 include a power-on ("ON")indicator 196a, an "OK" indicator 196b, a "BUSY" indicator 196c, a"READY" indicator 196d, and a "SERVICE" indicator 196e. The "OK"indicator 196b shows whether it is okay to insert or remove a cartridgeor a magazine, and the service indicator 196eshows whether thestackloader needs service, such as when a cartridge is stuck. The "BUSY"indicator 196c signifies that a cartridge 24 is being processed. The"READY" indicator 196d denotes that the rail 70 is locked into thecartridges 24 and that the stackloader is ready for operation. Morespecifically, the READY indicator 196d is illuminated when both of thefollowing conditions exist: (1) the ready sensor 193 is activated (i.e.,depressed as discussed above), and (2) the locking solenoid 194 isactivated (i.e., the locking pin is in the locking position 194b).

The switches 197 preferably include switches or other user entry devicesmarked to provide an "ON/OFF" switch 197a and a "PAUSE" switch 197b. ThePAUSE switch 197b allows an operator to stop the operation of thestackloader so the operator can insert or remove a cartridge withrespect to the magazine. The switches 197, the locking solenoid 194, andthe visual indicators 196 may be operated through the autochangercontroller logic 43 shown in FIG. 10.

FIG. 5 shows a right side of the stackloader with the plug 32 pluggedinto the slot 34 of the computer with a majority of the right coverplate removed except for a small portion shown at 64. A right supportplate 86 is vertically mounted in the housing 30 and the plug 32 forsupporting components which move the magazine 40 vertically within thehousing 30. The support plate 86 has front and rear vertical slots 88and 90 which are parallel with respect to one another. Mounted on themagazine 40 or a tray (not shown) for supporting the magazine are frontand rear sets of rollers 92 and 94 which ride up and down in thevertical slots 88 and 90, respectively, as the magazine 40 is moved upand down by a vertical movement device to be described in detailhereinafter. The support plate 86 has an intermediate vertical slot 96between the vertical slots 88 and 90. A pin 98 is fixed to a belt 100which connects the pin 98 to a pulley 102 of an incremental motor 104via top and bottom pulleys 106 and 108, which align the belt along theslot 96, and an intermediate pulley 110 which returns the belt to thepulley 102. The pulleys 106, 108, and 110 and the motor 104 are mountedto the support plate 86. The motor 104 is operatably connected to theautochanger controller 42 and is controlled thereby which will bedescribed in more detail hereinafter. FIG. 5 also illustrates the rail70 recessed in the vertical column of notches 60, the notch 72 which isaligned with an opening 112 in the drive 26, and the right tab 74 whichis also aligned with the opening 112 of the drive.

FIG. 6 is an enlarged illustration of the magazine 40 shown out of thehousing of the stackloader with one disk 24 shown therein forexplanatory purposes. The magazine 40 has a plurality of horizontallyextending receptacles 114, each receptacle being capable of slidablysupporting a respective cartridge 24. Each receptacle has front and rearopen ends 116 and 120 so that an operator can insert or removecartridges through the openings 120 and the cartridges can be insertedinto the opening of the drive 26 (see FIG. 5) through the front opening116. As can be seen from FIG. 6, the cartridge 24 extends rearwardlyfrom the rear opening 120 so that the notches 60 and 62 can formvertical columns of notches which are exposed for processing, the rightcolumn of notches being clearly seen at 60 in FIG. 5. The right notch 60receives the rail 70, as seen in FIG. 5, for locking purposes, asexplained hereinabove, and the left notch 62 is employed with ahorizontal picker device which will be explained in more detailhereinbelow. Each receptacle 114 has a respective horizontal slot 122which is also employed by the horizontal picker device. The magazine 40is exemplary and it should be understood that it can be configured indifferent sizes for different sizes of media.

FIG. 7 is an illustration of the left side of the stackloader with theplug 32 plugged into the slot 34 of the personal computer 38. The leftcover plate 66 has been removed to illustrate a left support plate 124which supports a horizontal movement device which functions as a pickerfor inserting and withdrawing a cartridge with respect to the drive 26.The horizontal movement device includes the support plate 124 having apair of horizontally extending top and bottom spaced apart slots 126 and128 which extend in both the housing and plug regions of thestackloader. The horizontal movement device further includes a rack andpinion 130 and 132, the pinion 132 which are driven by a motor 134, themotor 134 being connected to the autochanger controller 42 to bedescribed in more detail hereinafter. The rack may include top andbottom horizontally extending bars 136 and 138 which carry top andbottom pins 140 and 142, the pins slidably riding in the top and bottomhorizontal slots 126 and 128. A vertical plate 144 interconnects thehorizontal bars 136 and 138 and extends therebelow adjacent the leftcolumn of cartridge notches 62. Connected on an opposite side of thevertical plate 144 is the engagement block 82 (see FIG. 3) which isreceived by the vertical column of left notches 62 of the cartridges asthe magazine 40 moves up and down within the housing 30. It should benoted once again that the engagement block 82 is horizontally alignedwith the opening 112 of the drive 26 of the personal computer.

In FIG. 7 a top cartridge in the magazine is shown in a retractedposition with respect to the drive 26. In FIG. 8 the top cartridge isshown horizontally moved into the drive 26 for processing purposes. Thehorizontal movement has been implemented by the motor 134 and its pinion132 which advances the rack 130 forwardly. This causes the engagementblock 82 to advance the top cartridge forwardly into the drive, thedetent riding within the top slot 122 of the magazine 40. The reverseprocess takes place to return the cartridge to its retracted positionwithin the magazine, whereupon the magazine can be moved verticallyagain to align another selected cartridge with the opening 112 of thedrive for processing.

Shown schematically in FIGS. 7, 8 and 5 are dots which represent varioussensors for sensing the operational status of the stackloader. Infraredemitters and sensors can be employed to sense various conditions. Forinstance, an emitter 146 and a sensor 148 in the way of the verticalplate 144 of the horizontal movement device sense the Horizontal HomePosition of a vertical plate 144. An emitter 150 (see FIG. 5) and asensor 152 (see FIGS. 7 and 8) in the way of the bottom of the magazine40 sense the bottom or Vertical Home Position of the magazine 40. Anemitter 154 and a sensor 156 (see FIG. 7) in the way of the processingpath of a cartridge will detect that a cartridge is in this path andprevents the vertical movement of the magazine.

Sensor 158 is employed for identifying the type of magazine, themagazine's ID, and the type of media housed by the magazine. In thisregard, the sensor 158 may comprise one or multiple sensors for readingthis information. Magazines can have multiple media types.

This sensor senses this information from binary markings 162 on thecorner of the magazine as schematically illustrated in FIG. 6. Thebinary markings may comprise reflective sensors, bar codes, other binarymarkings, or even other non-binary machine-readable markings. All ofthese sensors and emitters can be mounted on the innersides of thecoverplates 64 and 66 (see FIG. 4).

A block diagram for an exemplary autochanger controller 42 isillustrated in FIG. 9. It consists of a microprocessor NVRAM, EPROM,drive interface logic for handshaking, a SCSI interface and autochangercontrol logic 43. Details of the autochanger control logic 43 is shownin FIG. 10. Standard SCSI commands are received over the SCSI interface,stored in the NVRAM and are interpreted by the microprocessor. Theprogram is stored in the EPROM. The microprocessor then writes controlinformation into the Z register 176, the X register 177 and register 202in the autochanger control logic (FIG. 10) to move cartridges to andfrom the drives. Sense information is determined by reading register188.

The autochanger controller 16 is connected to the motherboard 46 of thecomputer via the SCSI 48 as shown in FIG. 1. As is typical, themotherboard 46 includes a microprocessor (not shown) which is coupled tothe SCSI 48. As shown in FIG. 10, vertical move logic for the Zdirection is generally shown at 170 and horizontal move logic for the Xdirection is generally shown at 172. Since the vertical and horizontallogic are essentially the same, the description will be directed only tothe vertical move logic 170. All signals to and from the autochangerlogic control 43 are received through drivers and receivers 174. Themicroprocessor of the computer writes to a Z register 176 with a countand a direction. The count represents the extent to which the magazineis to be moved vertically within the housing of the stackloader and thedirection indicates whether the magazine is to move up or down. Thecontents of the register 176 are transferred to a counter 178 and adirection latch 180. The counter 178 decrements and causes a pulsegenerator 182 to send one pulse to the Z motor 104 for each counterdecrement via a driver 184. The Z motor 104 is an incremental motorwhich moves one increment for each count. The motor 104 moves themagazine up or down depending upon the contents of the direction latch180. When the counter 178 reaches zero, the output of a decoder 186 iszero which indicates that the operation has been completed. Thisindication is transferred to a register 188. This condition, as well asall conditions of the operation of the autochanger control logic 43 canbe read by the microprocessor in the autochanger controller 42 bypolling. The microprocessor also reads the status of sensors andswitches generally shown at 190 via receiver 192 and the register 188,the sensors being described hereinabove. These sensors include, forexample, the switches 197, as well as the sensors 148, 152, 156, and158.

The operation of the locking solenoid 194 and visual indicators (e.g.LEDs) 196 are also controlled by the microprocessor via drivers 198 and200, respectively, and via a register 202 and drivers and receivers 174.

The chart entitled "Mode Select Command for Drive/MediaCharacteristics", shown in Table 1 hereinbelow, explains how thestackloader can be adapted to handle different media for different drivetypes.

                  TABLE 1    ______________________________________    "Mode Select Command for Drive/Media Characteristics"    ______________________________________    Drive 1 Type    Loader of Drive 1 in Stepper Increments to Vertical Home Position    Drive 1 Horiz, Travel in Stepper Increments to Horizontal Home Position    Drive 2 Type    Loader of Drive 2 in Stepper Increments to Vertical Home Position    Drive 2 Horiz, Travel in Stepper Increments to Horizontal Home Position    Centerline of Media #1 to Vertical Home Position                            Cell Type    Centerline of Media #2 to Vertical Home Position                            Cell Type    .                       .    .                       .    .                       .    Centerline of Media #N to Reference Point                            Cell Type    ______________________________________

The stackloader uses the ANSI standard library command set. For example,a move command has a source and a destination. The source is theposition of the media in the stackloader and the destination is thedrive loader opening. A new mode select command would allow themicroprocessor of the personal computer to set the media location, thehorizontal travel, the media quantity, cell type and location of theopening to the drive with respect to the media location. This allows thestackloader to use different media types in the same magazine ordifferent magazines in the same stackloader. It also offers theflexibility to reconfigure the stackloader to function with future drivetypes. Multiple magazines may be put into the stackloader. The keymechanical parameter information would be sent to the stackloader usingthe mode select command as shown in the above chart.

Assuming that the computer has two different drive types, such as anoptical drive 26 and a floppy drive 28, as illustrated in FIG. 1, andthat different cartridges are required to be moved different horizontaldistances into a drive type, the microprocessor is programmed to knowthe number of stepper increments to move the magazine vertically and thenumber of stepper increments to move a cartridge horizontally for eachtype of drive and each type of cartridge employed in the system.Further, the microprocessor is programmed with the distance inincrements from the vertical centerline of each cartridge to a referencepoint and the type of cartridge involved. Accordingly, the stackloadercan handle all different kinds of media and drive types. The stackloadercan be adapted to handle multi magazines with each magazine having thesame media or multi media types.

In the embodiment of the stackloader described hereinabove, thehorizontal cartridge picker apparatus does not insert the wholecartridge into the drive, as illustrated in FIG. 8. In anotherembodiment of the stackloader, the horizontal picker device may bemodified to push a standard cartridge completely within the drive andafter processing push the standard eject button (not shown) on apersonal computer to return the cartridge to the horizontal pickerdevice. This would require a somewhat more complex horizontal pickerdevice, and therefore, the horizontal picker apparatus describedhereinabove is preferred. With the preferred picker, a portion of thecartridge is outside of the drive during processing.

What has been described is a stackloader that plugs into a full or halfhigh 51/4 inch slot in the front of a personal computer which has one ormore drives in one or more slots therebelow. A vertical moving device isemployed to move a magazine up and down within the stackloader so that acartridge can be aligned with an opening in a selected drive. Ahorizontal moving device moves the cartridge into and out of the drive.An autochanger controller accepts commands from the motherboard of thepersonal computer via a SCSI interface which is standard in mostpersonal computers. Either cartridges or magazines can be entered orremoved from the stackloader. Further, commands can be made whichconfigure the stackloader to accept various types of magazines andcartridges based upon a certain number of incremental movementshorizontally and vertically. The operator can insert or removecartridges from a magazine within the stackloader while the stackloaderis not in an active status.

The stackloader described hereinabove receives power from the personalcomputer. An alternate configuration would be a standalone stackloader204 illustrated in FIG. 12. In this embodiment the stackloader plugsinto a housing which includes an optical drive and a floppy drive withits own power source. The autochanger controller is interfaced with apersonal computer via the SCSI interface.

Operation

In addition to the hardware environment described above, the presentinvention also includes a method for operating a pluggable stackloader.FIGS. 11 and 13-17 depict different aspects of an exemplary operationalsequence for carrying out the method of the invention.

In an illustrative embodiment of the invention, these sequences may beimplemented by one or more hardware devices of the system 10 executingvarious lines of computer-executable instructions. These instructionsmay reside in some storage component of the system 10, for example, suchas RAM (not shown) of the executing hardware device. Alternatively, theinstructions may be contained on a data storage medium, such as acomputer diskette 1800 (FIG. 18). Alternatively, the instructions may bestored on a DASD array, magnetic tape, conventional "hard drive",electronic read-only memory, optical storage device, paper "punch"cards, or another data storage device. In an illustrative embodiment ofthe invention, the computer-executable instructions may comprise lines(not shown) of compiled C++ language code.

Overall Data Access Routine

In the invention's preferred embodiment, data access may be performedaccording to the sequence generally illustrated in FIG. 13. Thissequence, which includes a number of tasks 1300, manages the system'scartridges and magazines by performing various operations, such as (1)adding or removing cartridges from magazines, (2) auditing magazineinventory, and (3) facilitating cartridge data access, such as readingdata from cartridges and writing data to cartridges.

To discuss the routine 1300 in greater detail, reference is made to FIG.13. The routine 1300 is performed by various components of the system 10(FIG. 1A) in cooperation with each other, as discussed below. Theroutine 1300 is initiated by the host computer 38, and particularly thehost operating system 11, in response to receipt of a data accesscommand in task 1304. The data access command comprises a commandrequesting some type of access to cartridges housed or accessible by thestackloader 20. In one scenario, the data access command may beoriginally entered by a operator, using the keyboard display 50 torequest access to the stackloader's storage media. In a differentscenario, the data access command may be originally supplied by the hostcomputer 38 or another computer, such as the LAN-connected computer 21.Computer-originated data access commands may result, for example, from aneed for data occurring within the application program 12.

Preferably, the command received in task 1304 includes a command-typeand an operand. The command-type specifies a particular type of storageaccess operation, such as ADD, REMOVE, AUDIT, READ, or WRITE, in theillustrated example. The operand identifies a desired object forperforming the access operation, e.g. a file. The operand includes anumber of fields, which may differ for different operations, as shownbelow.

READ/WRITE Commands

With READ or WRITE commands, the operand includes the magazine, volumeidentifier ("vol-id"), subdirectory, filename, and filename extension,assembled in the following form:

    drive:\ {magazine\} vol-id\ {subdirectory\} filename.ext

The "drive" field identifies the stackloader 20 against other storagedevices such as the fast-access storage unit 15. The "magazine" fieldidentifies the magazine 22 that contains the desired cartridge. Themagazine field may comprise, for example, an alphanumeric name uniquelydistinguishing the desired magazine from other magazines. Since themagazine field is optional, it is shown in brackets. The "vol-id" fieldidentifies a storage "volume" containing the desired file. The volumemay encompass a part of one cartridge, an entire cartridge, or evenmultiple cartridges. In the illustrated embodiment, each vol-idcorresponds to one cartridge, and each cartridge's vol-id is alsorecorded as an item of data on the storage media of that cartridge.

The "subdirectory" field identifies a subdirectory on the volume wherethe desired file resides. In one embodiment, with multi-cartridgevolumes, different subdirectories may refer to different media types,e.g. one subdirectory corresponding to a 120 mm optical medium containedin the magazine, and another subdirectory corresponding to a 60 mmoptical medium contained in the magazine. The subdirectory field isshown in brackets, since it is optional. The "filename.ext" fieldcomprises an alphanumeric sequence identifying the desired file, and maycomprise a filename compatible with the well known disk operating system("DOS").

ADD Commands

With ADD commands, the operand is assembled in the following form:

    drive:\ vol-id \magazine\ receptacle

The "receptacle" field specifies the magazine receptacle 114 intendedfor receipt of a cartridge to be added.

REMOVE Commands

With REMOVE commands, the operand is assembled in the following form:

    drive:\ vol-id \magazine

AUDIT Commands

With AUDIT commands, the operand is assembled in the following form:

    drive: magazine-1 magazine-2, . . . magazine-N

Each term in the operand, such as "magazine-1", identifies a differentmagazine that is targeted for auditing, in the same order. If nomagazine is specified, the currently mounted magazine is audited.

If the command received in task 1304 is entered manually via thekeyboard display 50, the magazine and subdirectory components may beomitted, for the convenience of the operator. If the magazine identifieris omitted, the command is considered to refer to the magazine currentlymounted in the stackloader 20. If the subdirectory is omitted, the rootdirectory is referenced as a default.

Preferably, the inventory (not shown) is stored on the fast-accessstorage unit 15 (FIG. 1A), or another quickly accessible and reliablestorage location. The inventory lists all cartridges in the system 10,lists all magazines 22 in the system 10, and indexes each cartridge tothe magazine containing that cartridge.

Having received the data access command in task 1304 from the operator,the application program 12, or another source such as a LAN-connectedcomputer 21, the host operating system 11 performs query 1306. In query1306, the host operating system 11 asks whether the command hasrequested access to data managed by the stackloader 20. In theillustrated example, this data is stored on optical media. If thereceived data access command seeks data other than optical data, such asdata contained in the fast-access storage unit 15, the host operatingsystem 11 executes the requested data access in task 1308, withoutinvolving the stackloader 20.

However, if the received data access command seeks data managed by thestackloader 20, the host operating system 11 passes control to thestackloader controller 14. The stackloader controller 14 then performsappropriate ones of queries 1310, 1314, 1318, and 1322 to determine whatcommand-type was specified in the data access command.

More particularly, in query 1310 the stackloader controller 14determines whether the received command was an ADD command, i.e. acommand to add a new cartridge to a magazine. If so, the controller 14performs the ADD routine (described below) in task 1312 and then returnsto task 1304 to await receipt of another data access command.

If the data access command is not an ADD command, query 1310 directscontrol to query 1314, in which the stackloader controller 14 determineswhether the received command was a REMOVE command, i.e. a command toremove an existing cartridge from a magazine. If so, the controller 14performs the REMOVE routine (described below) in task 1316 and thenreturns to task 1304 to await receipt of another data access command.

If the data access command is not an ADD or REMOVE command, queries 1310and 1314 direct control to query 1318, in which the stackloadercontroller 14 determines whether the received command was an AUDITcommand, i.e. a command to review the status of the cartridge andmagazine inventory. If so, the controller 14 performs the AUDIT routine(described below) in task 1320 and then returns to task 1304 to awaitreceipt of another data access command.

If the data access command is not an ADD, REMOVE, or AUDIT command,queries 1310, 1314, and 1318 direct control to query 1322, in which thestackloader controller 14 determines whether the received command was aREAD or WRITE command, i.e. a command to read data from, or write datato, an existing cartridge. If so, the controller 14 performs theREAD/WRITE routine (described below) in task 1324 and then returns totask 1304 to await receipt of another data access command. As anexample, the ADD 1312, REMOVE 1316, AUDIT 1320, and READ/WRITE 1324routines may be implemented as separate subroutines.

In the illustrated system 10, if the data access command is notidentified as an ADD, REMOVE, AUDIT, or READ/WRITE command, an error hasoccurred. Accordingly, in task 1326 an error message is generated andsent to the source of the faulty data access command, e.g. the keyboarddisplay 50, application program 12, host operating system 11,LAN-connected computer 21, or other source.

Add Operation

In the invention's preferred embodiment, ADD operations may be performedaccording to the sequence generally illustrated in FIG. 14. Thissequence, which includes a number of tasks 1400, generally functions toreceive a "target cartridge" into one of the magazines 22 and log thecartridge's identity and location into the inventory.

The ADD routine 1400 is largely performed by the stackloader controller14. The routine 1400, which corresponds to task 1312 (FIG. 13), startsin task 1402 when query 1310 (FIG. 13) determines that an ADD dataaccess command has been issued. As mentioned above, an ADD data accesscommand includes a drive, vol-id, magazine, and receptacle. In query1404, the stackloader controller 14 determines whether the vol-idspecified in the data access command appears in inventory. If so, then"adding" this cartridge is not possible, since it is already present inthe system 10; in this case, an error message is issued in task 1406,and the routine 1400 exits in task 1408.

However, if a new vol-id has been specified by the data access command,the stackloader controller 14 goes to query 1410 to determine whetherthe data access command specified a magazine in which to add the targetcartridge. If not, the stackloader controller 14 in task 1412 selects afree magazine receptacle 114 in a currently-loaded magazine. After task1412, or an affirmative answer to query 1410, the stackloader controller14 in task 1414 asks whether the stackloader 20 is currently coupled tothe magazine that was (1) previously specified in a data access command,or (2) selected in task 1412, as applicable. If the magazine is notalready mounted, the stackloader controller 14 in task 1416 calls uponan operator interface routine 1100 (FIG. 11) to manage the loading ofthe required magazine into the stackloader 20. The operator interfaceroutine 1100 is described in greater detail below.

With the required magazine mounted, control passes to task 1417, whichcalls upon the operator interface routine 1100 (FIG. 11) to manage theloading of the target cartridge. The operator interface routine 1100provides for insertion of the target cartridge into the receptaclespecified in the data access command. As described below, the operatorinterface routine 1100 also illuminates the indicator 195a that isadjacent to the specified receptacle, to aid the operator in insertingthe target cartridge into the correct receptacle.

After the target cartridge is added, the stackloader controller 14 andthe autochanger controller 16 in task 1418 cooperatively fetch thetarget cartridge. In task 1420, the controllers 14/16 mount the targetcartridge to the drive 26 and read the vol-id contained thereon.

Then, in query 1422, the stackloader controller 14 verifies that thevol-id found in task 1420 agrees with the vol-id listed in inventory forthat cartridge. If these vol-ids do not match, an error message isissued in task 1424, and the routine ends in task 1408. If the vol-idsagree, however, the stackloader controller 14 in task 1426 updates theinventory to reflect the addition of the target cartridge, and theroutine 1400 ends in task 1408.

As an alternative to portions of the routine 1400 described above, theoriginal ADD data access command may omit the vol-id of the cartridge tobe added. In this case, the cartridge's vol-id may be learnednonetheless during task 1420 when the controllers 14/16 mount thecartridge to the drive 26 and read the vol-id contained thereon.Moreover, the ADD routine 1400 may be modified by an ordinarily skilledartisan (having the benefit of this disclaimer) to provide for theaddition of magazines, as well as cartridges, to the stackloader 20.

Remove Operation

In the invention's preferred embodiment, REMOVE operations may beperformed according to the sequence generally illustrated in FIG. 15.Although not shown, the REMOVE command alternatively may facilitate theremoval of an entire magazine in addition to the removal of singlecartridges. This sequence, which includes a number of tasks 1500,generally oversees removal of a target cartridge from one of themagazines 22, as well as withdrawal of the listing for the cartridge ininventory.

The REMOVE routine 1500 is largely performed by the stackloadercontroller 14. The routine 1500, which corresponds to task 1316 (FIG.13), starts in task 1502 when query 1314 (FIG. 13) determines that aREMOVE data access command has been issued. As mentioned above, a REMOVEcommand includes a drive, vol-id, and magazine. In query 1504, thestackloader controller 14 determines whether the vol-id specified in thedata access command appears in inventory. If not, then "removing" thiscartridge is not possible, since it is not present in the system 10; inthis case, an error message 1506 is issued, and the routine 1500 exitsin task 1514.

However, if a valid vol-id has been specified by the data accesscommand, the stackloader controller 14 goes on to query 1508 todetermine whether the magazine containing the target cartridgecorresponding to the specified vol-id is presently mounted to thestackloader 20. To do this, the presently mounted magazine is identifiedby operating the sensor 158 to read the marking 162 (FIGS. 6, 8) on thecurrently-mounted magazine, and then cross-referencing the marking tothe inventory. Alternatively, if the presently mounted magazine haspreviously be identified using the sensor 158 during initial loading ofthe magazine or another operation, the identification of the magazinemay be skipped, as well as the cross-referencing step if alreadyperformed. In either case, if the magazine containing the targetcartridge is not already mounted, the autochanger controller 16 in task1510 performs the operator interface routine 1100 (described below, FIG.11) to manage the loading of the required magazine into the stackloader20.

After task 1510, or an affirmative answer to query 1508, the autochangercontroller 16 in task 1511 again performs the operator interface routine1100 (FIG. 11) to permit the operator to remove the target cartridge. Asdescribed below, the operator interface routine 1100 also illuminatesthe indicator 195a that is adjacent to the receptacle 114 containing thetarget cartridge, to aid the operator in removing the target cartridgefrom the correct receptacle.

After task 1511, the stackloader controller 14 in task 1512 updates theinventory to reflect the absence of the target cartridge. The routine1500 then ends in task 1514.

It will also be apparent to ordinarily skilled artisans (having thebenefit of this disclosure) that the REMOVE routine 1500 may be modifiedto provide for the removal of magazines, as well as cartridges, from thestackloader 20.

Audit Operation

In the invention's preferred embodiment, AUDIT operations may beperformed according to the sequence generally illustrated in FIG. 16.This sequence, which includes a number of tasks 1600, generally operatesto determine which receptacles in each magazine contain a cartridge, andfor each cartridge, what vol-id(s) reside on that cartridge.

The AUDIT routine 1600 is largely performed by the stackloadercontroller 14, with assistance from the autochanger controller 16. Theroutine 1600, which corresponds to task 1320 (FIG. 13), starts in task1602 when query 1318 (FIG. 13) determines that a AUDIT data accesscommand has been issued. Alternatively, or additionally, the AUDITroutine 1600 may be performed automatically whenever a magazine orcartridge is inserted into the stackloader 20; advantageously, thisensures that any new cartridge or magazine is automatically logged intothe inventory, and made available to any other host computers having LANlinks to the stackloader 20.

As mentioned above, an AUDIT command includes a drive and one or moremagazine identifiers. Task 1601 begins with the first specified magazine(or another predetermined cartridge), using the stackloader controller14 to determine whether this magazine is present. If not, theautochanger controller 16 in task 1603 performs the operator interfaceroutine 1100 (FIG. 11). to obtain and mount the specified magazine.After task 1603 or a positive answer to query 1601, as applicable, thestackloader controller 14 in query 1604 determines whether thecurrently-mounted magazine is valid, i.e. corresponds to a magazinelisted in inventory. If not, an error message is issued in task 1606 andthe routine ends in task 1608. The magazine's validity is determined byfirst operating the sensor 158 to read the markings 162 (FIGS. 6, 8) onthe magazine to obtain the magazine's identifier. Then, the stackloadercontroller 14 attempts to cross-reference the marking with the inventorylisting. Alternatively, if the presently mounted magazine has previouslybeen identified using the sensor 158 during initial loading of themagazine or another operation, the identification of the magazine may beskipped, as well as the cross-referencing step if already performed.

If the magazine is found valid, the autochanger controller 16 in task1610 mounts a first one of the cartridges contained in the magazine. Asan example, the first cartridge may be the top-most or bottom-mostcartridge, or another predetermined cartridge. After the optical drive27 reads the mounted cartridge's vol-id in task 1612, the stackloadercontroller 14 in task 1614 compares the vol-id with the vol-id listed ininventory for that cartridge. If the stackloader controller 14 in query1616 finds that these two vol-ids do not agree, the stackloadercontroller 14 in task 1618 notes the error in an error log maintained ina suitable storage location of the system 10.

After task 1618, or an affirmative answer to query 1616, the stackloadercontroller 14 asks in query 1620 whether all cartridges in the magazinehave been processed, i.e. by performing tasks 1610-1618. If morecartridges in the magazine remain, the stackloader controller 14 selectsanother cartridge in task 1622. This cartridge may be selected, forexample, by progressing through all cartridges present in the magazinein a predetermined pattern, e.g. top-down, or bottom-up. After task1622, control returns to task 1610 and proceeds from there as describedabove.

If query 1620 determines that all cartridges in the current magazinehave been processed, control advances to query 1621, where thestackloader controller 14 determines whether all magazines that wereoriginally specified in the data access command have been processed. Ifso, the routine ends in task 1608. Otherwise, the next magazine isobtained and mounted when the autochanger controller 16 executes theoperator interface routine 1100 (FIG. 11) in task 1623. After task 1623,control returns to task 1610, and proceeds as discussed above.

Read/Write Routine

In the invention's preferred embodiment, READ and WRITE operations maybe performed according to the sequence generally illustrated in FIG. 17.This sequence, which includes a number of tasks 1700, generallyfunctions to orchestrate mounting of a cartridge designated for a Reador Write operation, and then to perform Read or Write operations to thecartridge using the storage drive 26.

The READ/WRITE routine 1700 is performed by the stackloader controller14 in cooperation with the autochanger controller 16. The routine 1700,which corresponds to task 1324 (FIG. 13), starts in task 1702 when query1322 (FIG. 13) determines that an READ or WRITE data access command hasbeen issued. As mentioned above, a complete data access command includesa drive, magazine, subdirectory, and filename. In query 1704, thestackloader controller 14 determines whether the vol-id specified in thedata access command appears in inventory. If not, then reading orwriting data from/to this cartridge is not possible; in this case, anerror message 1706 is issued, and the routine 1700 exits in task 1724.

However, if the cartridge corresponding to the specified vol-id appearsin inventory, control advances to query 1708. In query 1708, thestackloader controller 14 consults the inventory to identify themagazine containing the desired cartridge, and then determines whetherthis magazine is currently mounted in the stackloader 20. Whether theappropriate magazine is mounted in inventory can be determined by usingthe sensor 158 to read the marking 162 (FIGS. 6, 8) on thecurrently-mounted magazine. Alternatively, if the presently mountedmagazine has previously been identified using the sensor 158 duringinitial loading of the magazine or another operation, the identificationof the magazine may be skipped, as well as the cross-referencing step ifalready performed. In either case, if the desired magazine is notcurrently mounted, the stackloader controller 14 in task 1710 calls uponthe operator interface routine 1100 (FIG. 11) to manage the loading ofthe required magazine into the stackloader 20. The operator interfaceroutine 1100 is described in greater detail below.

With the required magazine mounted, control passes to tasks 1712 and1714, in which the autochanger controller 16 directs the stackloader 20to fetch and then mount the desired cartridge. Also in task 1714, thestackloader controller 14 operates the drive 26 to read the vol-idcontained on the mounted cartridge. The stackloader controller 14 inquery 1716 then verifies that the vol-id read in task 1714 correspondsto the vol-id listed in inventory for that cartridge. If the two vol-idsdo not match, an error message is issued in task 1706.

If the vol-ids match, however, this means that the desired cartridge andthe presently mounted cartridge are one and the same. Accordingly, intask 1718 the stackloader controller 14 operates the drive to search themounted cartridge for the path (e.g. subdirectory) and filenamespecified previously specified in the READ/WRITE data access command. Inthe case of a READ command, the stackloader controller 14 in query 1720verifies that the desired file is present on the mounted cartridge. Inthe case of a WRITE command, the stackloader controller in query 1720verifies that the mounted cartridge contains the desired path andsufficient free space to receive the new file; of course, the desiredfile need not exist on the cartridge yet, since the WRITE command seeksto place it there. Unsuccessful verification of query 1720 leads to anerror message in task 1706, and exiting from the program 1700 in task1724. In contrast, successful verification leads to task 1722, where thestackloader controller 14 operates the drive 26 to exchange data usingthe drive 26, thereby carrying out the applicable Read or Writeoperations. After task 1722, the routine 1700 ends in task 1724.

Operator Interface Routine

In the invention's preferred embodiment, the operator interface routinemay be performed according to the sequence generally illustrated in FIG.11. This sequence, which includes a number of tasks 1100, generallyoperates to oversee insertion and removal of cartridges from magazinesmounted into the stackloader 20, as well as the insertion and removal ofthe magazines themselves. The handling of the cartridges and magazinesmay be performed by a human operator, with assistance from the system10.

The routine 1100, which is preferably performed by the autochangercontroller 16, is initiated in response to requests from the stackloadercontroller 14 submitted during the ADD 1400, REMOVE 1500, and READ/WRITE1600 routines, as described above. After the routine 1100 is initiated,the operator presses the pause button 197b (FIG. 4A) in task 1102; afterany ongoing stackloader operations complete, the stackloader 20 is heldin a wait state for initiation of the desired cartridge or magazineaccess.

More particularly, in query 1104 the autochanger controller 16determines whether the magazine is being moved, up or down to access,mount, or demount a particular cartridge as described above. If so,query 1106 waits until the magazine move is complete. Then, after themove is complete, or alternatively after a negative answer to query1104, the autochanger controller 16 in task 1108 inhibits any furthermagazine movement.

After task 1108, query 1110 determines whether any one of the cartridgesin the magazine is being moved in or out of the drive 26 by thestackloader 20 as described above. If so, query 1112 waits until thecartridge move is complete. Then, after the move is complete, oralternatively after a negative answer to query 1110, the autochangercontroller 16 in task 1114 inhibits any further cartridge movement.

After tasks 1108 and 1114, the stackloader 20 is effectively held in await state, preventing machine-initiated cartridge or magazine movement,and awaiting the operator's manual cartridge or magazine transfer.Particularly, the autochanger controller 16 in task 1116 illuminates theOK indicator 196b, which signifies that it is okay to insert or remove acartridge or magazine. If the routine 1100 is being performed forinsertion or removal of a cartridge, then in task 1116 the autochangercontroller 16 sends a predetermined signal to the indicator strip 195 toilluminate the indicator 195a positioned next to the appropriatemagazine receptacle 114. Alternatively, if a magazine exchange is totake place at a particular stackloader in a multiple stackloader system,all indicators 195a of the indicator strip 195 at the particularstackloader may be illuminated simultaneously to aid the operator inconducting the magazine exchange there. Also in task 1116, theautochanger controller 16 de-activates the locking solenoid 194, therebypermitting opening of the rail 70 and flange 74 for access to thecartridges or the magazine contained in the stackloader 70. Thedeactivation of the locking solenoid 194 likewise deactivates the READYindicator 195d, signifying that the rail 70 is no longer locked in placeand the stackloader is not ready for operation.

Next, the operator in task 1118 pivotally opens the rail 70 by graspingand swinging the tab 80. When the operator opens the rail 70, thistriggers the ready sensor 193; no action is taken in response, however,because the autochanger controller 16 has already de-activated the READYindicator 196d in task 1116.

Next, in task 1120, the operator is permitted to add or remove one ormore cartridges, or to remove the entire magazine and substitute adifferent magazine. In task 1122, the operator closes the rail 70 byreturning the tab 80 to its original position. This de-activates theready sensor 193, signalling the autochanger controller 16 that the rail70 is closed. However, the READY indicator 196d is not illuminated yetsince the locking solenoid has not been activated. In task 1124 theautochanger controller 16 activates the locking solenoid 194 to hold therail 70 in place. Also in task 1124, the autochanger controller 16 turnsoff the OK indicator 196b, signifying that it is no longer okay toinsert or remove the magazine or a cartridge. Furthermore, if anyindicator 195a of a strip 195 have been illuminated, the autochangercontroller 16 de-activates the illuminated indicator 195a in the case ofa cartridge access, or deactivates all indicators in the case of amagazine access. Also in task 1124, the autochanger controller 16illuminates the READY indicator 196d, denoting that the rail 70 is nowlocked into the cartridges and that the stackloader is ready foroperation. Accordingly, the stackloader 20 now permits horizontal andvertical movement of cartridges, e.g. cartridge movement performedduring mounting and de-mounting the cartridges. In task 1126, theroutine 1100 ends, returning to the routine 1400, 1500, 1600, or 1700that originally summoned the operator interface routine 1100.

Mode Selection Commands

As discussed above, the present invention also contemplates a number ofmode selection commands, such as the following: (1) definition of thedrive and media type in the stackloader, (2) setting the increments forthe stackloader media, (3) setting horizontal travel for different mediatypes, (4) setting the media storage receptacle increments in thestackloader, (5) setting the number of media receptacles in thestackloader, and (6) locating the opening of the drive with respect tothe media in the magazine. An alternative to the SCSI interface with theautochanger controller is to employ a microchannel which would send SCSIcommands over the microchannel interface to operate the stackloader.

Other Embodiments

Obviously, other embodiments and modifications of the invention willoccur to those of ordinary skill in the art in view of the aboveteachings. Therefore, the invention is to be limited only by thefollowing claims, which include all of such embodiments andmodifications when viewed in conjunction with the above specificationand accompanying drawings.

What is claimed is:
 1. A method of operating a pluggable stackloadingsystem that includes:a digital data storage drive to exchange data witha media item mounted to the drive, the media item comprising a cartridgedefining a pair of opposing edges having corresponding first and secondoppositely disposed notches defined therein; a pluggable stackloader fortransporting media to and from the storage drive, including:astackloader housing including front and rear sides; a media magazinehaving a plurality of receptacles for slidably supporting a plurality ofcartridges, each receptacle having an open end, wherein the first andsecond notches of the cartridges are substantially vertically alignedwhen the cartridges are supported in the magazine; a movement mechanismto receive and mount a media magazine and individually transport andcouple to the drive selected cartridges supported by the mountedmagazine; and a controller coupled to the movement mechanism; saidmethod comprising the steps of:maintaining an inventory that identifiesa number of magazines associated with the stackloader, identifies allcartridges associated with the stackloader, and associates eachparticular cartridge with a magazine containing that particularcartridge; receiving an ADD command including specification of afilename and a vol-id; determining whether the specified vol-id appearsin the inventory, and if so issuing an error message and aborting,otherwise continuing; if the command did not specify a magazine,applying a predetermined selection process to specify a magazine;choosing an empty receptacle in the specified magazine; if the specifiedmagazine is not already mounted to the stackloader, operating thestackloader to receive and mount the specified magazine; the operatorinserting into the chosen receptacle a cartridge to be added; operatingthe stackloader to fetch the received cartridge from the currentlymounted magazine and mount the fetched cartridge to the drive; operatingthe drive to read a vol-id stored on the mounted cartridge; determiningwhether the vol-id matches the vol-id appearing in the ADD command, andif not issuing an error message and aborting, otherwise updating theinventory to reflect addition of the added cartridge.
 2. The method ofclaim 1, wherein the stackloader further comprises:a rail pivotallyconnected to the stackloader housing for selectively pivoting into thesecond notches of a plurality of vertically aligned cartridges supportedin the magazine to selectively lock the cartridges in the magazine, saidrail riding in the second notches during vertical movement of themagazine; an operator panel including at least one indicator to providevisual information to a human operator in response to an input signalfrom the controller, said operator panel also including at least oneoperator-activated switch to receive operator input and provide arepresentative output signal to the controller; and a locking solenoidresponsive to input signals from the controller to selectively lock andunlock the rail into and out of the second notches of cartridgessupported in the magazine, to lock and unlock the cartridges in themagazine;the steps of operating the stackloader to receive and mount thespecified magazine comprising the steps of: waiting until any ongoingmagazine movement by the stackloader is completed; inhibiting thestackloader from initiating any magazine movement; waiting until anyongoing cartridge movement by the stackloader is completed; inhibitingthe stackloader from initiating any cartridge movement; transmitting apredetermined input signal from the controller to the locking solenoidto deactivate the solenoid and unlock the rail; transmitting apredetermined input signal from the controller to the operator panel toactivate a first indicator signifying that a magazine exchange by theoperator is permitted; the operator pivotally opening the rail; theoperator inserting the specified magazine to the stackloader; theoperator closing the rail; transmitting a predetermined input signalfrom the controller to the locking solenoid to activate the solenoid andlock the rail; and transmitting a predetermined input signal from thecontroller to the operator panel to deactivate the first indicatorsignifying that magazine exchange by the operator is not permitted. 3.The method of claim 2, the pluggable stackloader additionally includinga selectively activated indicator strip proximate the housing, and themethod steps further comprising, prior to the operator pivotally openingthe rail, the steps of activating the indicator strip to direct theoperator to the stackloader.
 4. The method of claim 1, wherein thestackloader further comprises:a rail pivotally connected to thestackloader housing for selectively pivoting into the second notches ofa plurality of vertically aligned cartridges supported in the magazineto selectively lock the cartridges in the magazine, said rail riding inthe second notches during vertical movement of the magazine; an operatorpanel including at least one indicator to provide visual information toa human operator in response to an input signal from the controller,said operator panel also including at least one operator-activatedswitch to receive operator input and provide a representative outputsignal to the controller; and a locking solenoid responsive to inputsignals from the controller to selectively lock and unlock the rail intoand out of the second notches of cartridges supported in the magazine,to lock and unlock the cartridges in the magazine; an indicator strippositioned proximate the stackloader housing including multipleindicators selectively and individually activated in response to aninput signal from the controller, each indicator being exclusivelyassociated with one of the receptacles by being positioned adjacentthereto;the steps of operating the stackloader to receive and mount acartridge to be added comprising the steps of: waiting until any ongoingmagazine movement by the stackloader is completed; inhibiting thestackloader from initiating any magazine movement; waiting until anyongoing cartridge movement by the stackloader is completed; inhibitingthe stackloader from initiating any cartridge movement; transmittinginput signal from the controller to the locking solenoid to deactivatethe solenoid and unlock the rail; transmitting a predetermined inputsignal from the controller to the operator panel to activate a firstindicator signifying that operator insertion of a cartridge ispermitted; the operator pivotally opening the rail; transmitting apredetermined input signal from the controller to the indicator strip toactivate an indicator associated with the chosen receptacle; theoperator inserting a cartridge to be added into the chosen receptacle;the operator closing the rail; transmitting a predetermined input signalfrom the controller to the locking solenoid to activate the solenoid andlock the rail; and transmitting a predetermined input signal from thecontroller to the operator panel to deactivate the first indicatorsignifying that cartridge exchange by the operator is not permitted. 5.A method of operating a pluggable stackloading system that includes:adigital data storage drive to exchange data with a media item mounted tothe drive, the media item comprising a cartridge defining a pair ofopposing edges having corresponding first and second oppositely disposednotches defined therein; a pluggable stackloader for transporting mediato and from the storage drive, including:a stackloader housing includingfront and rear sides; a media magazine having a plurality of receptaclesfor slidably supporting a plurality of cartridges, each receptaclehaving an open end, wherein the first and second notches of thecartridges are substantially vertically aligned when the cartridges aresupported in the magazine; a movement mechanism to receive and mount amedia magazine and individually transport and couple to the driveselected cartridges supported by the mounted magazine; a controllercoupled to the movement mechanism;said method comprising the steps of:maintaining an inventory that identifies a number of magazinesassociated with the stackloader, identifies all cartridges associatedwith the stackloader, and associates each particular cartridge with amagazine containing that particular cartridge; receiving a REMOVEcommand including specification of a vol-id, said vol-id beingassociated with a particular cartridge; determining whether thespecified vol-id appears in the inventory, and if not issuing an errormessage and aborting, otherwise continuing; determining whether aspecific magazine containing the cartridge identified by the specifiedvol-id is currently mounted to the stackloader; if the specific magazineis not already mounted to the stackloader, operating the stackloader toreceive and mount the specific magazine; the operator removing thecartridge identified by the specified vol-id from the mounted magazine;and updating the inventory to reflect removal of the cartridgeidentified by the specified vol-id.
 6. The method of claim 5, whereinthe stackloader further comprises:a rail pivotally connected to thestackloader housing for selectively pivoting into the second notches ofa plurality of vertically aligned cartridges supported in the magazineto selectively lock the cartridges in the magazine, said rail riding inthe second notches during vertical movement of the magazine; an operatorpanel including at least one indicator to provide visual information toa human operator in response to an input signal from the controller,said operator panel also including at least one operator-activatedswitch to receive operator input and provide a representative outputsignal to the controller; and a locking solenoid responsive to inputsignals from the controller to selectively lock and unlock the rail intoand out of the second notches of cartridges supported in the magazine,to lock and unlock the cartridges in the magazine;the steps of operatingthe stackloader to receive and mount the specified magazine comprisingthe steps of: waiting until any ongoing magazine movement by thestackloader is completed; inhibiting the stackloader from initiating anymagazine movement; waiting until any ongoing cartridge movement by thestackloader is completed; inhibiting the stackloader from initiating anycartridge movement; transmitting a predetermined input signal from thecontroller to the locking solenoid to deactivate the solenoid and unlockthe rail; transmitting a predetermined input signal from the controllerto the operator panel to activate a first indicator, signifying thatmagazine exchange by the operator is permitted; the operator pivotallyopening the rail; the operator inserting the specific magazine to thestackloader; the operator closing the rail; transmitting a predeterminedinput signal from the controller to the locking solenoid to activate thesolenoid and lock the rail; and transmitting a predetermined inputsignal from the controller to the operator panel to deactivate the firstindicator signifying that magazine exchange by the operator is notpermitted.
 7. The method of claim 6, the pluggable stackloaderadditionally including a selectively activated indicator strip proximatethe housing, and the method steps further comprising, prior to theoperator pivotally opening the rail, the steps of activating theindicator strip to direct the operator to the stackloader.
 8. The methodof claim 5, wherein the stackloader further comprises:a rail pivotallyconnected to the stackloader housing for selectively pivoting into thesecond notches of a plurality of vertically aligned cartridges supportedin the magazine to selectively lock the cartridges in the magazine, saidrail riding in the second notches during vertical movement of themagazine; an operator panel including at least one indicator to providevisual information to a human operator in response to an input signalfrom the controller, said operator panel also including at least oneoperator-activated switch to receive operator input and provide arepresentative output signal to the controller; and a locking solenoidresponsive to input signals from the controller to selectively lock andunlock the rail into and out of the second notches of cartridgessupported in the magazine, to lock and unlock the cartridges in themagazine; an indicator strip positioned proximate the stackloaderhousing including multiple indicators selectively and individuallyactivated in response to an input signal from the controller, eachindicator being exclusively associated with one of the receptacles bybeing positioned adjacent thereto;the steps of operating the stackloaderto receive and mount a cartridge to be added comprising the steps of:waiting until any ongoing magazine movement by the stackloader iscompleted; inhibiting the stackloader from initiating any magazinemovement; waiting until any ongoing cartridge movement by thestackloader is completed; inhibiting the stackloader from initiating anycartridge movement; transmitting a predetermined input signal from thecontroller to the operator panel to activate a first indicatorsignifying that operator removal of a cartridge is permitted;transmitting a predetermined input signal from the controller to thelocking solenoid to deactivate the solenoid and unlock the rail; theoperator pivotally opening the rail; transmitting a predetermined inputsignal from the controller to the indicator strip to activate anindicator associated with the chosen receptacle; the operator removing acartridge identified by the specified vol-id from the chosen receptacle;the operator closing the rail; transmitting a predetermined input signalfrom the controller to the locking solenoid to activate the solenoid andlock the rail; and transmitting a predetermined input signal from thecontroller to the operator panel to deactivate the first indicatorsignifying that cartridge exchange by the operator is not permitted. 9.A method of operating a pluggable stackloading system that includes:adigital data storage drive to exchange data with a media item mounted tothe drive, the media item comprising a cartridge defining a pair ofopposing edges having corresponding first and second oppositely disposednotches defined therein; a pluggable stackloader for transporting mediato and from the storage drive, including:a stackloader housing includingfront and rear sides; a media magazine having a plurality of receptaclesfor slidably supporting a plurality of cartridges, each receptaclehaving an open end, wherein the first and second notches of thecartridges are substantially vertically aligned when the cartridges aresupported in the magazine; a movement mechanism to receive and mount amedia magazine and individually transport and couple to the driveselected cartridges supported by the mounted magazine;a controllercoupled to the movement mechanism;said method comprising the steps of:maintaining an inventory that identifies a number of magazinesassociated with the stackloader, identifies all vol-ids associated withthe stackloader, and associates each vol-id with a magazine containingthat cartridge; receiving an AUDIT command; sensing a machine-readablemarking contained on a magazine currently mounted to the stackloader;determining whether a magazine identifier corresponding to the sensedmarking appears in the inventory, and if not issuing an error messageand aborting, otherwise continuing; operating the stackloader tosequentially mount each cartridge present in the currently mountedmagazine and for each particular cartridge performing stepscomprising:operating the storage drive to read a vol-id stored on theparticular cartridge; comparing the read vol-id with a vol-idrepresented in the inventory as being associated with thecurrently-mounted magazine; and if the compared vol-ids do not match,recording an error message in an error log.
 10. A method of operating apluggable stackloader system that includes:a digital data storage driveto exchange data with a media item mounted to the drive, the media itemcomprising a cartridge defining a pair of opposing edges havingcorresponding first and second oppositely disposed notches definedtherein; a pluggable stackloader for transporting media to and from thestorage drive, including:a stackloader housing including front and rearsides; a media magazine having a plurality of receptacles for slidablysupporting a plurality of cartridges, each receptacle having an openend, wherein the first and second notches of the cartridges aresubstantially vertically aligned when the cartridges are supported inthe magazine; a movement mechanism to receive and mount a media magazineand individually transport and couple to the drive selected cartridgessupported by the mounted magazine; a controller coupled to the movementmechanism;said method comprising the steps of: maintaining an inventorythat identifies a number of magazines associated with the stackloader,identifies all cartridges associated with the stackloader, andassociates each particular cartridge with a magazine containing thatparticular cartridge; receiving a READ/WRITE command includingspecification of a filename and a vol-id; determining whether thespecified vol-id appears in the inventory, and if not issuing an errormessage and aborting, otherwise continuing; determining whether specifica magazine containing the cartridge identified by the specified vol-idis currently mounted to the stackloader; if the magazine is not alreadymounted to the stackloader, operating the stackloader to receive andmount the specific magazine; operating the stackloader to fetch theidentified cartridge from the currently mounted magazine and mount thefetched cartridge to the drive; reading the vol-id of the mountedcartridge; determining whether the read vol-id matches the vol-idspecified by the READ/WRITE command, and if not issuing an error messageand aborting and otherwise continuing; operating the storage drive toexchange data with the mounted cartridge in accordance with the receivedREAD/WRITE command.
 11. The method of claim 10, the READ/WRITE commandcomprising a WRITE command.
 12. The method of claim 10, the READ/WRITEcommand comprising a READ command.
 13. The method of claim 10, the stepof operating the storage drive to exchange data comprising the steps ofwriting a file having the specified filename to the mounted cartridge.14. The method of claim 10, the step of operating the storage drive toexchange data comprising the steps of updating a file having thespecified filename in the mounted cartridge.
 15. The method of claim 10,the step of operating the storage drive to exchange data comprising thesteps of reading a file having the specified filename from the mountedcartridge.
 16. The method of claim 10, wherein the stackloader furthercomprises:a rail pivotally connected to the stackloader housing forselectively pivoting into the second notches of a plurality ofvertically aligned cartridges supported in the magazine to selectivelylock the cartridges in the magazine, said rail riding in the secondnotches during vertical movement of the magazine; an operator panelincluding at least one indicator to provide visual information to ahuman operator in response to an input signal from the controller, saidoperator panel also including at least one operator-activated switch toreceive operator input and provide a representative output signal to thecontroller; and a locking solenoid responsive to input signals from thecontroller to selectively lock and unlock the rail into and out of thesecond notches of cartridges supported in the magazine, to lock andunlock the cartridges in the magazine;the steps of operating thestackloader to receive and mount the specified magazine comprising thesteps of: waiting until any ongoing magazine movement by the stackloaderis completed; inhibiting the stackloader from initiating any magazinemovement; waiting until any ongoing cartridge movement by thestackloader is completed; inhibiting the stackloader from initiating anycartridge movement; transmitting a predetermined input signal from thecontroller to the operator panel to activate a first indicatorsignifying that magazine exchange by the operator is permitted;transmitting a predetermined input signal from the controller to thelocking solenoid to deactivate the solenoid and unlock the rail; theoperator pivotally opening the rail; the operator inserting the specificmagazine; the operator closing the rail; transmitting a predeterminedinput signal from the controller to the locking solenoid to activate thesolenoid and lock the rail; and transmitting a predetermined inputsignal from the controller to the operator panel to deactivate the firstindicator signifying that magazine exchange by the operator is notpermitted.
 17. The method of claim 16, the pluggable stackloaderadditionally including a selectively activated indicator strip proximatethe housing, and the method steps further comprising, prior to theoperator pivotally opening the rail, the steps of activating theindicator strip to direct the operator to the stackloader.
 18. A methodof operating a pluggable stackloading system that includes:a digitaldata storage drive to exchange data with a media item mounted to thedrive, the media item comprising a cartridge defining a pair of opposingedges having corresponding first and second oppositely disposed notchesdefined therein; a pluggable stackloader for transporting media to andfrom the storage drive, including:a stackloader housing including frontand rear sides to receive a media magazine having a plurality ofreceptacles for slidably supporting a plurality of cartridges, eachreceptacle having an open end, wherein the first and second notches ofthe cartridges are substantially vertically aligned when the cartridgesare supported in the magazine; a movement mechanism to receive and mounta media magazine and individually transport and couple to the driveselected cartridges supported by the mounted magazine; a controllercoupled to the movement mechanism; and a magazine sensor to readmagazine an identifier contained on a magazine mounted to thestackloader;said method comprising the steps of: maintaining aninventory that identifies a number of magazines associated with thestackloader; receiving an ADD command including identification of amagazine; determining whether the identified magazine is listed in theinventory, and if so issuing an error message and aborting, otherwisecontinuing; if the identified magazine is not already mounted to thestackloader, operating the stackloader to receive and mount theidentified magazine; operating the magazine sensor to read a magazineidentifier provided by the presently mounted magazine; and using themagazine identifier to determine whether the mounted magazine is themagazine identified in the ADD command, and if not issuing an errormessage and aborting, otherwise updating the inventory to reflectaddition of the added magazine.
 19. The method of claim 18, wherein thestackloader further comprises:a rail pivotally connected to thestackloader housing for selectively pivoting into the second notches ofa plurality of vertically aligned cartridges supported in the magazineto selectively lock the cartridges in the magazine, said rail riding inthe second notches during vertical movement of the magazine; an operatorpanel including at least one indicator to provide visual information toa human operator in response to an input signal from the controller,said operator panel also including at least one operator-activatedswitch to receive operator input and provide a representative outputsignal to the controller; and a locking solenoid responsive to inputsignals from the controller to selectively lock and unlock the rail intoand out of the second notches of cartridges supported in the magazine,to lock and unlock the cartridges in the magazine;the steps of operatingthe stackloader to receive and mount the specified magazine comprisingthe steps of: waiting until any ongoing magazine movement by thestackloader is completed; inhibiting the stackloader from initiating anymagazine movement; waiting until any ongoing cartridge movement by thestackloader is completed; inhibiting the stackloader from initiating anycartridge movement; transmitting a predetermined input signal from thecontroller to the operator panel to activate a first indicatorsignifying that a magazine exchange by the operator is permitted;transmitting a predetermined input signal from the controller to thelocking solenoid to deactivate the solenoid and unlock the rail; theoperator pivotally opening the rail; the operator inserting thespecified magazine to the stackloader; the operator closing the rail;transmitting a predetermined input signal from the controller to thelocking solenoid to activate the solenoid and lock the rail; andtransmitting a predetermined input signal from the controller to theoperator panel to deactivate the first indicator signifying thatmagazine exchange by the operator is not permitted.
 20. A method ofoperating a pluggable stackloading system that includes:at least onedigital data storage drive to exchange data with a media item mounted tothe drive, the media item comprising a cartridge defining a pair ofopposing edges having corresponding first and second oppositely disposednotches defined therein; multiple pluggable stackloaders fortransporting media to and from the at least one storage drive, eachstackloader including:a stackloader housing including front and rearsides to receive a media magazine having a plurality of receptacles forslidably supporting a plurality of cartridges, each receptacle having anopen end, wherein the first and second notches of the cartridges aresubstantially vertically aligned when the cartridges are supported inthe magazine; a movement mechanism to receive and mount a media magazineand individually transport and couple to the drive selected cartridgessupported by the mounted magazine; a controller coupled to the movementmechanism; a magazine sensor to read magazine an identifier contained ona magazine mounted to the stackloader; and a selectively activatedindicator proximate the housing;said method comprising the steps of:maintaining an inventory that identifies a number of magazinesassociated with the stackloaders; receiving an ADD command includingidentification of a magazine; determining whether the identifiedmagazine is listed in the inventory, and if so issuing an error messageand aborting, otherwise continuing; if the identified magazine is notalready mounted to a stackloader and the command did not identify astackloader at which to add the identified magazine, performing stepscomprising:applying a predetermined selection process to specify astackloader; activating the indicator of the specified stackloader; andoperating the stackloader to receive and mount the identified magazine;operating the magazine sensor to read a magazine identifier provided bythe presently mounted magazine; and using the magazine identifier todetermine whether the mounted magazine is the magazine identified in theADD command, and if not issuing an error message and aborting, otherwiseupdating the inventory to reflect addition of the added magazine.
 21. Amethod of operating a pluggable stackloading system that includes:adigital data storage drive to exchange data with a media item mounted tothe drive, the media item comprising a cartridge defining a pair ofopposing edges having corresponding first and second oppositely disposednotches defined therein; a pluggable stackloader for transporting mediato and from the storage drive, including:a stackloader housing includingfront and rear sides to receive a media magazine having a plurality ofreceptacles for slidably supporting a plurality of cartridges, eachreceptacle having an open end, wherein the first and second notches ofthe cartridges are substantially vertically aligned when the cartridgesare supported in the magazine; a movement mechanism to receive and mounta media magazine and individually transport and couple to the driveselected cartridges supported by the mounted magazine; a controllercoupled to the movement mechanism;said method comprising the steps of:maintaining an inventory that identifies a number of magazinesassociated with the stackloader; receiving a REMOVE command includingidentification of a magazine; determining whether the identifiedmagazine is listed in the inventory, and if not issuing an error messageand aborting, otherwise continuing; the operator removing the identifiedmagazine from the stackloader; and updating the inventory to reflectremoval of the specified magazine.
 22. The method of claim 21, whereinthe stackloader further comprises:a rail pivotally connected to thestackloader housing for selectively pivoting into the second notches ofa plurality of vertically aligned cartridges supported in the magazineto selectively lock the cartridges in the magazine, said rail riding inthe second notches during vertical movement of the magazine; an operatorpanel including at least one indicator to provide visual information toa human operator in response to an input signal from the controller,said operator panel also including at least one operator-activatedswitch to receive operator input and provide a representative outputsignal to the controller; and a locking solenoid responsive to inputsignals from the controller to selectively lock and unlock the rail intoand out of the second notches of cartridges supported in the magazine,to lock and unlock the cartridges in the magazine;the steps of operatingthe stackloader to receive and mount the specified magazine comprisingthe steps of: waiting until any ongoing magazine movement by thestackloader is completed; inhibiting the stackloader from initiating anymagazine movement; waiting until any ongoing cartridge movement by thestackloader is completed; inhibiting the stackloader from initiating anycartridge movement; transmitting a predetermined input signal from thecontroller to the operator panel to activate a first indicator,signifying that magazine exchange by the operator is permitted;transmitting a predetermined input signal from the controller to thelocking solenoid to deactivate the solenoid and unlock the rail; theoperator pivotally opening the rail; the operator inserting the specificmagazine to the stackloader; the operator closing the rail; transmittinga predetermined input signal from the controller to the locking solenoidto activate the solenoid and lock the rail; and transmitting apredetermined input signal from the controller to the operator panel todeactivate the first indicator signifying that magazine exchange by theoperator is not permitted.
 23. A method of operating a pluggablestackloading system that includes:at least one digital data storagedrive to exchange data with a media item mounted to the drive, the mediaitem comprising a cartridge defining a pair of opposing edges havingcorresponding first and second oppositely disposed notches definedtherein; multiple pluggable stackloaders for transporting media to andfrom the at least one storage drive, each stackloader including:astackloader housing including front and rear sides to receive a mediamagazine having a plurality of receptacles for slidably supporting aplurality of cartridges, each receptacle having an open end, wherein thefirst and second notches of the cartridges are substantially verticallyaligned when the cartridges are supported in the magazine; a movementmechanism to receive and mount a media magazine and individuallytransport and couple to the drive selected cartridges supported by themounted magazine; a controller coupled to the movement mechanism; and aselectively activated indicator proximate the housing;said methodcomprising the steps of: maintaining an inventory that identifies anumber of magazines associated with the stackloaders; receiving a REMOVEcommand including identification of a magazine; determining whether theidentified magazine is listed in the inventory, and if not issuing anerror message and aborting, otherwise continuing; determining whichstackloader contains the identified magazine; activating the indicatorof the stackloader containing the identified magazine; the operatorremoving the identified magazine from the stackloader containing theidentified magazine; and updating the inventory to reflect removal ofthe identified magazine.